Update docs on credentials for panic --> error.
Update docs on credentials for panic --> error.

mthjones/rusoto,DualSpark/rust-aws,mattico/rusoto,rusoto/rusoto,SecurityInsanity/rusoto,mattico/rusoto,cmsd2/rusoto,DualSpark/rusoto,mattico/rusoto,SecurityInsanity/rusoto,ford-prefect/rusoto,noggleboggle/rusoto,DualSpark/rusoto,rusoto/rusoto,rusoto/rusoto,DualSpark/rusoto,ford-prefect/rusoto,DualSpark/rust-aws,indiv0/rusoto,DualSpark/rust-aws,mthjones/rusoto